Bad service

Hi! At around July i ordered bedding that cost R3500,the order was cash and i payed immediately. After two weeks i called to enquire about my order,i was told that what i ordered is out of stock. I then told them to cancel the order and asked for my refund, i even faxed the deposit slip 4 times already but eeverytime i call their customer services they teld me they can't give me the answer concerning my refund because is not in their hands. I then decided not to pay the intalment as i have an account with them, so they called me to ask me when am i paying my instalment. I then told them to deduct the iinstalment from my refund, they told me to fax the deposit slip again i did but still they are unable to transfer the money to my account and they call me everyday to tell me my account is in arrears. I am so frustrated its like they want me to forfeit my money because no one is willing to help. Can u please help me to deal with this matter, please. Its almost 3 months now and they call me everyday to ask me about my instalment and i tell them about my refund, they tell me to fax, and i fax every week but nothing is happening.